Twisted or torque yarns are currently produced using a two-step process. Undrawn feeder yarn is spun in the first step using conventional spinning and winding equipment. The second step involves producing the final torque yarn by drawing and false-twisting of the feeder yarn on a separate piece of equipment. The predominant method for putting twist in the torque yarn is the friction-false-twist method. The draw-twist step typically occurs at 1000 meters/minute. The false-twisting is a four-stage process consisting of:
1) twisting a continuous filament yarn; PA1 2) heat-setting the yarn in a twisted configuration; PA1 3) cooling the yarn prior to releasing the twist; and PA1 4) untwisting the yarn in the opposite direction of the original twist. PA1 (a) melt-spinning a nylon yarn at a speed of more than 3000 m/min; PA1 (b) applying heat to the yarn; PA1 (c) cooling the yarn; PA1 (d) false twisting; and PA1 (e) winding the yarn.
Twisting of the yarn is accomplished by passing it over a moving surface with frictional characteristics high enough to rotate the yarn.
The JP 72036457 discloses a process for the manufacture of twisted yarn by simultaneously spinning, holding, twisting and drawing the yarn. The twisting occurs on a rotating cylinder at a temperature within the range from the glass transition point to a temperature 20.degree. C. below the polymer melting point. The drawing occurs with a drawing roll after the twisting. The highest disclosed spinning speed is 1,000 m/min.
U.S. Pat. No. 3,996,324 discloses a high speed single step process for producing pre-oriented synthetic yarn by using a pigtail guide and a horseshoe guide to produce an untwisted yarn in ribbon form and by taking up the yarn at a speed of from 2500 to 6000 meters per minute.
U.S. Pat. No. 4,726,180 discloses a false twist apparatus comprising a rotating cylinder with guides to set the yarn in a helix path around the cylinder which will enable yarns to be processed at low twist levels with consistency and good process control. The reference does not disclose a one step process for the manufacture of twisted yarn.
Object of the present invention was to provide a one step process for the manufacture of twisted nylon yarns which simultaneously spins, draws and false-twists a nylon yarn at winding speeds above 3000 m/min.